Field of the Invention
The present invention relates to a technique of processing substrates such as a semiconductor wafer, a glass substrate for liquid crystal display, a glass substrate for plasma display, a substrate for optical disc, a substrate for magnetic disk, a substrate for magneto-optical disk, a glass substrate for photomask, and a substrate for solar cell (hereinafter, merely referred to as “substrates”).
Description of the Background Art
A device pattern (circuit pattern) is not usually formed right up to the end face of a substrate, and in many cases, the device pattern is formed in the upper surface region located inside from the end face of the substrate by a constant width.
In the deposition step for forming a device pattern, however, a film may be formed up to the outside of the region in which a device pattern is formed (hereinafter, merely referred to as a “device region”). The film formed outside of the device region is not required and also can cause various malfunctions. For example, the film formed outside of the device region may peel off during the processing steps, reducing yields or causing malfunction in, for example, a substrate processing apparatus.
In consideration of the above, the process of removing a thin film formed outside of the device region by etching, or, so-called bevel etching process is performed in some cases, and apparatuses for performing such a process are proposed (for example, see Japanese Patent Application Laid-Open Nos. 2011-066194 and 2009-070946).
The apparatuses of Japanese Patent Application Laid-Open Nos. 2011-066194 and 2009-070946 discharge a processing liquid onto a peripheral portion of an upper surface of a substrate from nozzles arranged above the peripheral portion while rotating the substrate about the central axis in a horizontal plane, thereby processing the peripheral portion of the upper surface. The nozzles have outlets that are opposed to a part of the rotation path of the peripheral portion of the substrate from above. The nozzles continuously discharge a processing liquid such that the processing liquid comes into contact with the portion, which is located below the outlets, of the peripheral portion of the upper surface of the substrate being rotated. Each part of the peripheral portion of the upper surface repeatedly passes through below the nozzles, and each time, is supplied with a fresh processing liquid from the nozzles.
Japanese Patent Application Laid-Open Nos. 2005-142290, 2014-072389, and 2003-264168 describe the apparatuses that supply processing liquids such as various chemical solutions to an upper surface of a substrate while heating the substrate by a heater opposed to the substrate, thereby processing the substrate. Heating the substrate improves, for example, a processing rate.
The apparatus of Japanese Patent Application Laid-Open No. 2005-142290 includes a heater opposed to the peripheral portion of the upper surface of the substrate and another heater opposed to the peripheral portion of the lower surface of the substrate. The apparatus supplies a processing liquid to the central portion of the upper surface while heating the peripheral portion of the substrate by these heaters from above and below, thereby processing the entire upper surface. The apparatus of Japanese Patent Application Laid-Open No. 2014-072389 discharges a processing liquid onto the central portion of the upper surface of the substrate while heating the entire substrate by the heater opposed to the entire lower surface of the substrate, thereby processing the entire upper surface. The apparatus of Japanese Patent Application Laid-Open No. 2003-264168 discharges a processing liquid onto the peripheral portion of the upper surface of the substrate while heating the peripheral portion of the substrate by an annular heater opposed to the peripheral portion of the lower surface of the substrate, thereby processing the peripheral portion of the upper surface.
Japanese Patent Application Laid-Open No. 2004-79908 describes a substrate processing apparatus including an etching liquid supply nozzle and a pure water supply nozzle. The etching liquid supply nozzle discharges an etching liquid onto a plurality of positions of a peripheral portion of an upper surface of a substrate, which have different distances from the center of rotation of the substrate. The pure water supply nozzle discharges pure water for protection onto the central portion of the upper surface of the substrate. The pure water discharged onto the central portion of the upper surface is supplied to the entire upper surface by the rotation of the substrate and washes away the etching liquid dispersed in a to-be-protected region of the upper surface except for the peripheral portion. This protects the to-be-protected region. The etching liquid has a high concentration at the position with which the etching liquid comes into contact, and the etching liquid that has spread from that position toward the periphery is diluted with pure water and accordingly has a decreased concentration. For the etching process to advance uniformly at the respective positions with different radial distances from the center of rotation in the peripheral portion of the substrate, the apparatus of Japanese Patent Application Laid-Open No. 2004-79908 supplies an etching liquid to the plurality of positions with different distances from the center of rotation of the substrate, to thereby make the concentration of the etching liquid uniform in the peripheral portion of the substrate.
Japanese Patent Application Laid-Open No. 2003-86567 discloses a substrate processing apparatus including an etching liquid discharge nozzle and a rinse liquid discharge nozzle. The etching liquid discharge nozzle discharges an etching liquid such that the etching liquid comes into contact with the peripheral portion of the substrate. The rinse liquid discharge nozzle discharges a rinse liquid such that the rinse liquid comes into contact with the position of the substrate located on the side closer to the center of the substrate than the position with which the etching liquid comes into contact. The apparatus first positions both of the nozzles such that the etching liquid and the rinse liquid come into contact with two portions of the substrate closer to the center of the substrate, and then discharges the etching liquid and the rinse liquid from the respective nozzles, thereby performing an etching process. Subsequently, the apparatus stops discharging the etching liquid without changing the positions of the nozzles and continuously discharges the rinse liquid, thereby performing a rinse process. Subsequently, the apparatus moves the nozzles together toward the periphery of the substrate, thereby positioning the nozzles such that the rinse liquid comes into contact with the region from which the thin film has been removed by the first etching process and that the etching liquid comes into contact with the position on the side closer to the periphery of the substrate. The apparatus sequentially performs etching and rinse processes again after positioning. In the second rinse process, the rinse liquid comes into contact with the region from which the thin film has been removed. This prevents a situation in which the rinse liquid comes into contact with the thin film, and metal ions of the thin film flow out and adheres to the peripheral portion.
In the apparatuses of Japanese Patent Application Laid-Open Nos. 2011-066194 and 2009-070946, however, the respective parts of the peripheral portion of the upper surface arrive at the portion below the nozzle, with the processing liquid remaining in the respective parts. Thus, a processing liquid newly discharged from the nozzle (“fresh processing liquid”) comes into contact with the processing liquid (“residual processing liquid”) to cause splashes. When the splashed processing liquid enters the device region, a defect occurs in the device pattern.
When an inert gas is discharged at a high flow rate onto the landing position of the processing liquid in the peripheral portion of the upper surface of the substrate toward the upstream portion in the direction of rotation of the substrate, the residual processing liquid is blown off by a gas flow of an inert gas to be removed from the peripheral portion. This prevents a collision between the residual processing liquid and a fresh processing liquid. If an inert gas comes into contact with the residual processing liquid at a high flow rate, however, the residual processing liquid may splash to arrive at the device region.
If the flow rate of the inert gas is decreased to restrict the generation of splashes that can arrive at the device region, the residual processing liquid cannot be completely removed from the peripheral portion. As a result, a fresh processing liquid may come into contact with the residual processing liquid and cause splashes, and the splashed processing liquid may enter the device region.
According to Japanese Patent Application Laid-Open Nos. 2005-142290, 2014-072389, and 2003-264168, a space exists between the substrate and the heater, and as the substrate rotates, the room-temperature atmosphere existing around the peripheral portion of the substrate is taken into the space between the substrate and the heater. The substrate is cooled from the lower surface by the room-temperature atmosphere, which unfortunately decreases the heating efficiency of the substrate.
In the apparatuses of Japanese Patent Application Laid-Open Nos. 2004-79908 and 2003-86567, the etching liquid discharged onto the peripheral portion of the upper surface of the substrate wraps around the lower surface of the substrate. As a result, the lower surface of the substrate, which is not to be etched, may be etched, thus damaging the lower surface. In addition, the pure water and the rinse liquid that protect a to-be-protected region of the upper surface may dilute the etching liquid, decreasing the processing efficiency.